One of the steps in producing integrated circuit semiconductor chips is to project the image defined by a mask onto the surface of a semiconductor wafer. In order to achieve greater miniaturization of the integrated circuits of these chips methods have been sought to project smaller mask images while maintaining sharp and precise circuit lines. To achieve this end, lithographic techniques progressed from the use of visible and ultra-violet electromagnetic energy to "soft X-rays." Soft X-rays occupy that portion of the electromagnetic spectrum just above ultra-violet energy. The shorter wavelength of soft X-rays makes possible the projection of smaller mask images.
Hard X-rays have shorter wavelengths than soft X-rays and occupy that portion of the electromagnetic spectrum above soft X-rays. Gamma rays have wavelengths shorter than hard X-rays and occupy that part of the electromagnetic spectrum above hard X-rays. Thus, it would be desirable to utilize hard X-rays and gamma rays to project mask images to produce more minute chip circuitry.
A problem in attempting to use these shorter-wavelength electromagnetic energies (hard X-rays and gamma rays) is that useful manipulation is difficult because of the shorter wavelengths and high electrical energies involved. Standard focusing mechanisms, such as lenses and prisms, are ineffective.